I have been told by several diesel experts that diesel engines do not run hot when run lean, unlike gasoline engines.
In addition to retorquing the head bolts, you might try adding some of the brown color dry fiber pellets (I forget the brand name, it may be "Bars Leaks" ) that help seal small coolant leaks and head gasket leaks to your coolant.
I have used them for 30 years. A Chemical Engineer at Preston told me in 1995 that the OEM manufacturers have used, and added them to all new car radiators for about 80 years or more to make sure the cooling systems do not leak during the warranty period. If a small leak forms the fibers get stuck at the leak site, and the coolant drys up at the barrier, leaving a silicate (concrete) fiber seal at the leak point. The silicate is an acid neutralizer but also turns to a permanent solid (silica) at very hot leak spots like a small head gasket leak.
I may have retorque my SD22 (Nissan) diesel head bolts, after reading about your success with that trick, but mine passed a 10 minute head gasket leak test.
Mine does not overheat, but it also does not want to suck the coolant back into the radiator from the coolant overflow bottle (yes I know that sucks, LOL). I had a huge air problem in mine for 5 years, that I feared was the head gasket, but it turned out to be the water pump seal and water pump gasket on the suction side drawing in air . But it never leaked under pressure.
By the way, there is a diesel head gasket tester solution available that works with the typical "Block tester" rental kit from places like Advanced, AZ, and O'Rieleys. Part number 75730. Found at:
http://www.sjdiscounttools.com/lis-75730.html
There is a bulb on top of the block tester that you use to suck air out of the radiator and through the bubbler and fluid. 2 minute test will determine if there are combustion gasses in the radiator coolant. I tested mine for 10 minutes, with no color change, but I did not have it up to WOT on the freeway under a peak load, which is where an initial, small leak might start as the head pressures peak at WOT under heavy load.
In my case, I am just about convinced my problem is a radiator neck sealing problem, although I can not prove it, short of getting a new radiator. Or a very small leak in the oil cooler heat exchanger. So far I have no signs of leaks, into or out of the system. Just the annoying refusal of coolant to flow back into the radiator over night during cool down. Maybe it thinks it is a Renix closed system, LOL. But I may just retorque those head bolts for the hell of it.
In your case I would definately add some of those sealing pellets to help reseal that head gasket before it goes completely! I posted the part number for them here last year under in several threads. One of them was about snake oil fixes that actually work, IIRC.
I may have to track down that Bosch DVD you mentioned for fun some day. My Bosch is real interesting, it has a pneumatic over mechanical FI control on it. The SD22 is a naturally aspirated diesel. It operates the FIP on a throttle body plate differential vacuum combined with mechanical engine speed to control fuel rate flow.
Glad to hear you have that beast back on the road! Congrats!
Oh, and by the way, you have way too many posts here (only 43, LOL), especially for a 2005 joined up year.:laugh3: